Not applicable.
This invention relates generally to graft polyols and, more particularly, to preparation of graft polyols via a continuous process. The process includes the use of a minor amount of a pre-existing first graft polyol during formation of a final graft polyol.
Methods for the formation of graft polyols, also known as polymer polyols, are known in the art and typically involve the reaction of monomers with a macromer in the presence of a carrier polyol, a reaction moderator, and a free radical polymerization initiator wherein the monomers copolymerize with the macromer. One of the difficulties associated with current processes for preparing graft polyols is that the reactors tend to accumulate fouling, which is a particularly significant problem for continuous reactors. This fouling causes the reactors to quickly become plugged with sediment of unstable compounds in the reaction. Thus, one is required to shut down and clean the reactor leading to a loss in productivity of the reactor. Thus, it would be highly advantageous to create a continuous process for the formation of graft polyols having a reduced tendency for fouling.
In general terms, this invention provides a method of forming a graft polyol and a graft polyol formed by the method using a continuous process.
In one embodiment the invention comprises a continuous method for formation of a final graft polyol comprising the steps of: providing a first reaction stream comprising a first graft polyol having a vinyl polymer content of from 3 to 20 weight percent, a carrier polyol, a macromer having induced unsaturation, and at least one free radical polymerization initiator; providing a second reaction stream comprising at least two ethylenically unsaturated monomers and a reaction moderator; and combining the first reaction stream with the second reaction stream in a continuous reactor thereby continuously forming a final graft polyol having a solids level of from 30 to 70 weight percent.
In a second embodiment, the invention comprises a final graft polyol made by a continuous process and having a solids level of from 30 to 70 weight percent, the second graft polyol comprising the reaction product of at least two ethylenically unsaturated monomers, a reaction moderator, and a macromer having induced unsaturation in the presence of a carrier polyol, a first graft polyol having a vinyl polymer content of from 3 to 20 weight percent, and at least one free radical polymerization initiator.
In another embodiment, the invention comprises a continuous method for formation of a final graft polyol comprising the step of: reacting a first graft polyol having a vinyl polymer content of from 3 to 20 weight percent, a carrier polyol, a macromer having induced unsaturation, and at least one free radical polymerization initiator with at least two ethylenically unsaturated monomers and a reaction moderator in a continuous reactor thereby continuously forming a final graft polyol having a solids level of from 30 to 70 weight percent.
These and other features and advantages of this invention will become more apparent to those skilled in the art from the detailed description of a preferred embodiment. The drawings that accompany the detailed description are described below.